Hi Mithun - due to the lengthy backlog of work that we have we are loathe to cancel an application unless we have to. Conveyancers are given time to respond to any requests and can ask for more time as appropriate.
If there is no realistic chance of them satisfying the request and it is causing issues for later applications then you can contact us to advise of the specifics and ask us to consider as appropriate. If DLA don't respond within a given timeframe we may advise of your issues and explain no more time will be allowed
Either use our contact form yourself (you can ask for their contact details) or perhaps ask your own conveyancer to contact us or DLA direct to try and resolve matters -
Public guidance: dealing with land and property - GOV.UK